U.S. patent number 7,201,158 [Application Number 10/559,618] was granted by the patent office on 2007-04-10 for exhaust gas recirculation control device for diesel engine.
This patent grant is currently assigned to Yanmar Co., Ltd.. Invention is credited to Michihiko Hara, Akihiro Nishimura.
United States Patent |
7,201,158 |
Nishimura , et al. |
April 10, 2007 |
Exhaust gas recirculation control device for diesel engine
Abstract
An exhaust gas recirculation control device in a diesel engine,
capable of suppressing NOx and smoke discharged. A first
temperature sensor (11) is provided at a portion more on the
upstream side than a portion where a suction air path (3) joins an
exhaust gas recirculation path (4), and a second temperature sensor
(12) is provided on the downstream side. Further, an engine load
detection sensor (6) and an engine speed detection sensor (7) are
arranged. The exhaust gas recirculation control device also has
memory means where the temperature of suction air before it is
mixed with an exhaust gas and a temperature value at a second
temperature sensor installation position are previously memorized,
the temperature value corresponding to an appropriate exhaust gas
recirculation amount that is uniquely defined by an engine load and
an engine speed. Further, judging means is provided. The judging
means compares the corresponding temperature value memorized in the
memory means and a value detected by the second temperature sensor.
When the detected value is within a predetermined range relative to
the temperature value, a circulation exhaust gas amount is
determined to be appropriate, and when the detected value is not
within a predetermined range relative to the temperature value, a
circulation exhaust gas amount is determined to be abnormal.
Inventors: |
Nishimura; Akihiro (Osaka,
JP), Hara; Michihiko (Osaka, JP) |
Assignee: |
Yanmar Co., Ltd. (Osaka-shi,
JP)
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Family
ID: |
33508406 |
Appl.
No.: |
10/559,618 |
Filed: |
May 28, 2004 |
PCT
Filed: |
May 28, 2004 |
PCT No.: |
PCT/JP2004/007741 |
371(c)(1),(2),(4) Date: |
December 02, 2005 |
PCT
Pub. No.: |
WO2004/109088 |
PCT
Pub. Date: |
December 16, 2004 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20060144374 A1 |
Jul 6, 2006 |
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Foreign Application Priority Data
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Jun 3, 2003 [JP] |
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2003-157841 |
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Current U.S.
Class: |
123/568.16;
701/108; 701/114; 123/568.21; 73/114.31 |
Current CPC
Class: |
F02M
26/49 (20160201); F02M 26/47 (20160201); F02D
41/0052 (20130101); F02D 41/0072 (20130101); F02B
3/06 (20130101); F02D 2041/0067 (20130101); Y02T
10/40 (20130101); F02D 2200/0414 (20130101) |
Current International
Class: |
F02M
25/07 (20060101); F02B 47/08 (20060101); G01M
15/00 (20060101); G06F 19/00 (20060101) |
Field of
Search: |
;123/568.11,568.16,568.21-568.28 ;701/108,114,115
;73/117.3,118.1,118.2 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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55-116101 |
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Sep 1980 |
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JP |
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58-197461 |
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Nov 1983 |
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JP |
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62-162761 |
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Jul 1987 |
|
JP |
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63-038678 |
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Feb 1988 |
|
JP |
|
63-134844 |
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Jun 1988 |
|
JP |
|
63-259148 |
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Oct 1988 |
|
JP |
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2002-256982 |
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Sep 2002 |
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JP |
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Other References
International Search Report dated Sep. 14, 2004 (Five (5) Pages).
cited by other.
|
Primary Examiner: Wolfe, Jr.; Willis R.
Attorney, Agent or Firm: Crowell & Moring LLP
Claims
What is claimed is:
1. An exhaust gas recirculation control device in a diesel engine
provided with an exhaust gas recirculation path communicating a
suction air path with an exhaust gas path, the device comprising: a
first temperature sensor provided at a portion more on the upstream
side than a portion where said suction air path joins the exhaust
gas recirculation path; a second temperature sensor provided at a
portion more on the downstream side than a portion where said
suction air path joins the exhaust gas recirculation path; an
engine load detection sensor; an engine speed detection sensor;
memory means storing, in advance, a temperature of a suction air
before being mixed with an exhaust gas, and a temperature value at
said second temperature sensor installation position corresponding
to an appropriate exhaust gas recirculation amount which is
uniquely defined by an engine load and an engine speed; and judging
means comparing the temperature value stored in said memory means
corresponding to the detected values detected from said engine load
detection sensor, the engine speed detection sensor and the first
temperature sensor, with the detection value detected by said
second temperature sensor, determining that the recirculation
exhaust gas amount is appropriate in the case that said detection
value is within a predetermined range relative to said temperature
value, and determining that the recirculation exhaust gas amount is
abnormal in the case that said detection value is not within the
predetermined range relative to said temperature value.
2. An exhaust gas recirculation control device in a diesel engine
according to claim 1, wherein in the diesel engine in which an
operation of rapidly changing an engine load or an engine speed is
executed, said judging means executes a judgment of the amount of
the recirculation exhaust gas only at a time when the engine load
and the engine speed are stabilized.
3. An exhaust gas recirculation control device in a diesel engine
according to claim 1, wherein a cooling water temperature sensor
detecting a temperature of a cooling water is provided, a detecting
means detecting that a warm-up is finished on the basis of a fact
that the temperature of the cooling water detected by said cooling
water temperature sensor detects reaches a predetermined
temperature is provided, and the judgment of the amount of the
recirculation exhaust gas is executed by said judging means at
either a time after the warm-up is finished and before an actual
operation is started, or a time after the actual operation is
finished and the engine stops.
4. An exhaust gas recirculation control device in a diesel engine
according to claim 1, wherein when the judging means determines
that the amount of the recirculation exhaust gas is abnormal in the
case that the detection value does not exist within the
predetermined range, by comparing the temperature value stored in
said memory means corresponding to the detection value detected
from said engine load detection sensor, the engine speed detection
sensor and the first temperature sensor with the detection value
detected by said second temperature sensor, a margin in said
predetermined range is set smaller in a side in which the detection
value of the second temperature sensor is higher than in a side in
which the detection value is lower.
5. An exhaust gas recirculation control device in a diesel engine
according to claim 1, wherein a compensating means for compensating
the temperature value stored in said memory means by the
temperature value detected by said cooling water temperature sensor
at a time of a cooling condition is provided.
6. An exhaust gas recirculation control device in a diesel engine
according to claim 1, wherein a response delay of the detection
value by said second temperature sensor is compensated by averaging
the temperature value stored in said memory means corresponding to
the detection values detected from said engine load detection
sensor in a temporal manner, the engine speed detection sensor and
the first temperature sensor.
7. An exhaust gas recirculation control device in a diesel engine
according to claim 6, wherein a compensating means for compensating
the temperature value stored in said memory means by the
temperature value detected by said cooling water temperature sensor
at a time of a cooling condition is provided.
8. An exhaust gas recirculation control device in a diesel engine
according to claim 1, wherein a throttle valve capable of
regulating a flow rate of the exhaust gas passing through said
exhaust gas recirculation path is provided in the exhaust gas
recirculation path, a control means for controlling an opening
degree of said throttle valve is provided, and an opening degree of
the throttle valve is controlled by said control means, whereby the
temperature value at the portion more on the downstream side than
the portion where the suction air path communicates with said
exhaust gas recirculation path corresponding to the temperature
value at the portion more on the upstream side than the portion
where the suction air path communicates with said exhaust gas
recirculation path is within a previously set predetermined
range.
9. An exhaust gas recirculation control device in a diesel engine
according to claim 8, wherein a response delay of the detection
value by said second temperature sensor is compensated by averaging
the temperature value stored in said memory means corresponding to
the detection values detected from said engine load detection
sensor in a temporal manner, the engine speed detection sensor and
the first temperature sensor.
10. An exhaust gas recirculation control device in a diesel engine
according to claim 8, wherein in the diesel engine in which an
operation of rapidly changing an engine load or an engine speed is
executed, said judging means executes a judgment of the amount of
the recirculation exhaust gas only at a time when the engine load
and the engine speed are stabilized.
11. An exhaust gas recirculation control device in a diesel engine
according to claim 8, wherein a cooling water temperature sensor
detecting a temperature of a cooling water is provided, a detecting
means detecting that a warm-up is finished on the basis of a fact
that the temperature of the cooling water detected by said cooling
water temperature sensor detects reaches a predetermined
temperature is provided, and the judgment of the amount of the
recirculation exhaust gas is executed by said judging means at
either a time after the warm-up is finished and before an actual
operation is started, or a time after the actual operation is
finished and the engine stops.
12. An exhaust gas recirculation control device in a diesel engine
according to claim 8, wherein a compensating means for compensating
the temperature value stored in said memory means by the
temperature value detected by said cooling water temperature sensor
at a time of a cooling condition is provided.
Description
TECHNICAL FIELD
The present invention relates to an exhaust gas recirculation type
diesel engine which can suppress discharge of smoke and NOx.
BACKGROUND ART
(Prior Art)
In an operation environment surrounding a diesel engine, a
regulation is becoming severe in recent years, and it is desired to
provide a diesel engine having a performance which can satisfy the
regulation. Japanese Unexamined Patent Publication No. 63-134844
describes an exhaust gas recirculation type internal combustion
engine. In this publication, in order to avoid an increase of an
NOx discharging amount caused by a reduction of an EGR gas amount,
there is disclosed a technique of controlling so as to secure a
predetermined amount or more of EGR gas. The invention described in
No. 63-134844 relates to the internal combustion engine in which a
throttle valve is necessarily provided as a constituting element,
as described in claim 1 of No. 63-134844. In other words, although
No. 63-134844 describes the internal combustion engine, the
embodiment is described by exemplifying a gasoline engine, and the
throttle valve is described in FIG. 1. Accordingly, it is apparent
that the diesel engine is not included in the internal combustion
engine expressed in the invention of No. 63-134844.
No smoke (no soot) is discharged from the gasoline engine disclosed
in the publication mentioned above, and it is basically sufficient
to take a structure for preventing NOx from being discharged into
consideration. On the contrary, in the diesel engine, if an EGR gas
amount is increased, an NOx amount is reduced, but a discharge
amount of the smoke is increased. Accordingly, in the diesel
engine, it is impossible to uphold a control standard for the
exhaust gas even by applying the invention described in the patent
document 1.
In the exhaust gas recirculation type diesel engine, at a time of
controlling the EGR gas amount, it is necessary to regulate within
a range which can simultaneously suppress both the NOx amount and
the smoke amount discharged.
DISCLOSURE OF INVENTION
(Problems to be Solved by the Invention)
Accordingly, an object of the present invention is to provide an
exhaust gas recirculation control device for a diesel engine which
can simultaneously suppress both of discharged NOx and smoke by
controlling such that a rate of EGR becomes within a predetermined
range.
(Means for Solving the Problems)
In order to solve the problems mentioned above, in accordance with
a first aspect of the present invention, an exhaust gas
recirculation control device in a diesel engine provided with an
exhaust gas recirculation path communicating a suction air path
with an exhaust gas path, includes: a first temperature sensor
provided at a portion more on the upstream side than a portion
where the suction air path joins the exhaust gas recirculation
path; a second temperature sensor provided at a portion more on the
downstream side than a portion where the suction air path joins the
exhaust gas recirculation path; an engine load detection sensor; an
engine speed detection sensor; a memory means storing, in advance,
a temperature of a suction air before being mixed with an exhaust
gas, and a temperature value at the second temperature sensor
installation position corresponding to an appropriate exhaust gas
recirculation amount which is uniquely defined by an engine load
and an engine speed; and a judging means comparing the temperature
value stored in the memory means corresponding to the detected
values detected from the engine load detection sensor, the engine
speed detection sensor and the first temperature sensor, with the
detection value detected by the second temperature sensor,
determining that the recirculation exhaust gas amount is
appropriate in the case that the detection value is within a
predetermined range relative to the temperature value, and
determining that the recirculation exhaust gas amount is abnormal
in the case that the detection value is not within the
predetermined range relative to the temperature value.
In accordance with a second aspect of the present invention, the
structure is made in the invention as recited in the first aspect
such that a throttle valve capable of regulating a flow rate of the
exhaust gas passing through the exhaust gas recirculation path is
provided in the exhaust gas recirculation path, a control means for
controlling an opening degree of the throttle valve is provided,
and an opening degree of the throttle valve is controlled by the
control means, whereby the temperature value at the portion more on
the downstream side than the portion where the suction air path
communicates with the exhaust gas recirculation path corresponding
to the temperature value at the portion more on the upstream side
than the portion where the suction air path communicates with the
exhaust gas recirculation path is within a previously set
predetermined range.
In accordance with a third aspect of the present invention, the
structure is made in the invention as recited in the first or
second aspect such that a response delay of the detection value by
the second temperature sensor is compensated by averaging the
temperature value stored in the memory means corresponding to the
detection values detected from the engine load detection sensor in
a temporal manner, the engine speed detection sensor and the first
temperature sensor.
In accordance with a fourth aspect of the present invention, the
structure is made in the invention as recited in the first or
second aspect such that in the diesel engine in which an operation
of rapidly changing an engine load or an engine speed is executed,
the judging means executes a judgment of the amount of the
recirculation exhaust gas only at a time when the engine load and
the engine speed are stabilized.
In accordance with a fifth aspect of the present invention, the
structure is made in the invention as recited in the first or
second aspect such that a cooling water temperature sensor
detecting a temperature of a cooling water is provided, a detecting
means detecting that a warm-up is finished on the basis of a fact
that the temperature of the cooling water detected by the cooling
water temperature sensor reaches a predetermined temperature is
provided, and the judgment of the amount of the recirculation
exhaust gas is executed by the judging means at either a time after
the warm-up is finished and before an actual operation is started,
or a time after the actual operation is finished and the engine
stops.
In accordance with a sixth aspect of the present invention, the
structure is made in the invention as recited in the first aspect
such that when the judging means determines that the amount of the
recirculation exhaust gas is abnormal in the case that the
detection value does not exist within the predetermined range, by
comparing the temperature value stored in the memory means
corresponding to the detection value detected from the engine load
detection sensor, the engine speed detection sensor and the first
temperature sensor with the detection value detected by the second
temperature sensor, a margin in the predetermined range is set
smaller in a side in which the detection value of the second
temperature sensor is higher than in a side in which the detection
value is lower.
In accordance with a seventh aspect of the present invention, the
structure is made in the invention as recited in any one of the
first to third aspect such that a compensating means for
compensating the temperature value stored in the memory means by
the temperature value detected by the cooling water temperature
sensor at a time of a cooling condition is provided.
(More Effective Advantages than Prior Art)
In accordance with the first aspect of the present invention, since
an engine load detection sensor 6 and an engine speed detection
sensor 7 is provided for comprehending an operation condition of a
diesel engine 100, a memory means previously storing a downstream
temperature corresponding to an appropriate exhaust gas
recirculation amount which is uniquely defined by an upstream
temperature T.sub.1, an engine load and an engine speed is
provided, a first temperature sensor 11 detecting the upstream
temperature T.sub.1 and a second temperature sensor 12 detecting a
downstream temperature T.sub.2 are further provided, and a judging
means 13 for determining whether or not a temperature difference
between the both is within a predetermined range by comparing a
temperature value corresponding to an operation condition stored in
the memory means with the downstream temperature T.sub.2 detected
by the second temperature sensor 12 is provided, it is possible to
judge whether or not an EGR rate of the diesel engine 100 is
normal. Accordingly, it is possible to suppress the discharge of
both the NOx and the smoke until the abnormality is detected. When
the abnormality is detected, it is possible to seize an opportunity
for devising a countermeasure by stopping the operation or
generating an alarm.
It is possible to recognize a fluctuation of the EGR rate on the
basis of a clogging of a suction air filter 10 or a clogging of a
muffler 15, by carrying out the first aspect of the present
invention, whereby it is possible to appropriately determine a
timing for executing a maintenance.
In accordance with the second aspect of the present invention, it
is possible to control the EGR rate in such a manner as to suppress
a discharge amount of the smoke and the NOx, by arranging an EGR
valve 5 in an exhaust gas recirculation path 4, and regulating an
opening degree of the EGR valve 5 so as to control a downstream
temperature T.sub.2 within an appropriate range.
In accordance with the third aspect of the present invention, it is
possible to avoid an erroneous judgment of a judging device 13 by
executing a judgment using a temporal average while taking a delay
of detection of the second temperature sensor 12 into
consideration, the combustion fluctuation of the diesel engine 100
becomes small, and it is possible to well suppress a discharge
amount of the smoke and the NOx.
In accordance with the fourth aspect of the present invention,
since the amount of the recirculation exhaust gas is judged only at
a time when the engine load and the engine speed are stabilized, in
the diesel engine 100 in which the operation rapidly changing the
engine load or the engine speed is executed, it is possible to
avoid the combustion fluctuation at a time of the normal operation
of the diesel engine 100.
In accordance with the fifth aspect of the present invention, since
the judgment by the judging device 13 is executed after the warm-up
of the diesel engine 100 is sufficiently executed, by detecting
that the warm-up is finished on the basis of the fact that the
cooling water temperature reaches the predetermined temperature by
means of the cooling water temperature sensor 14 detecting the
temperature of the cooling water, it is possible to avoid the
judging work at a time of the cooling condition in which the
appropriate judgment is hard to be executed, and it is possible to
avoid the combustion fluctuation.
In accordance with the sixth aspect of the present invention, it is
possible to well suppress the discharge of the smoke by setting a
margin of the predetermined range smaller in the side in which the
detection value of the second temperature sensor 12 becomes higher
than in the side in which the detection value becomes lower, at a
time when the judging device 13 determines that the amount of the
EGR gas is abnormal in the case that the detection value detected
by the second temperature sensor 12 does not exist within the
predetermined range from the temperature value on the map stored in
the memory 19.
In accordance with the seventh aspect of the present invention,
since a compensation means for compensating the temperature value
stored in the memory 19 (the memory means) on the basis of the
temperature value detected by the cooling water temperature sensor
14 at a time of the cooling condition is provided, it is possible
to secure the appropriate EGR rate even at a time of the cooling
condition, and it is possible to reduce the discharge amount of the
smoke and the NOx.
BRIEF DESCRIPTION OF DRAWINGS
FIG. 1 is a schematic view of a system of a diesel engine obtained
by carrying out the present invention;
FIG. 2 is a graph which compares an example of an appropriate value
(a standard mixed gas temperature Ts) of a downstream temperature
T.sub.2 changing in correspondence to a change of an engine load
and an engine speed, with an upstream temperature T.sub.1;
FIG. 3 is a graph which compares a change of the downstream
temperature T.sub.2 actually measured by a second temperature
sensor, with a compensated mixed gas temperature Tmr corresponding
to an appropriate value of the downstream temperature on a map;
FIG. 4 is a graph showing a relation between an opening degree of
an EGR valve and the engine load;
FIG. 5 is a graph showing a change of the downstream temperature
T.sub.2 relative to a load fluctuation;
FIG. 6 is a graph comparing the fluctuation of the engine load with
the downstream temperature;
FIG. 7 is a graph showing a relation between an axial mean
effective pressure and an engine speed per the different EGR
rate;
FIG. 8 is a graph showing a relation between an exhaust gas
regulation allowable range limited by an allowable smoke amount and
an allowable NOx amount contained in the exhaust gas, and an EGR
rate of the diesel engine; and
FIG. 9 is a graph further compensating the compensated mixed gas
temperature Tmr while taking a cooling water temperature into
consideration.
DESCRIPTION OF THE PREFERRED EMBODIMENT
FIG. 1 is a schematic view of a system of a diesel engine 100
obtained by carrying out the present invention (each of the
inventions on the basis of the first to seventh aspects). The
diesel engine 100 is provided with a suction air path 3 having a
suction air filter 10 in the middle and supplying an air to a
combustion chamber 17 within an engine main body 1, and an exhaust
gas path 2 discharging an exhaust gas after combustion. A muffler
15 is provided in the exhaust gas path 2.
As shown in FIG. 1, one end of an exhaust gas recirculation path 4
is connected to the middle of the exhaust gas path 2, and the other
end of the exhaust gas recirculation path 4 is connected to the
suction air path 3 in a joint portion 9. An electromagnetic control
type EGR valve 5 (a throttle valve) is provided in the exhaust gas
recirculation path 4. An amount of exhaust gas (EGR gas) mixed with
an air in the joint portion 9 can be regulated by changing an
opening degree of the EGR valve 5.
Further, a fuel injection pump 16 supplying a fuel to the
combustion chamber 17 is provided in the diesel engine 100. An
engine load detection sensor 6 is provided in the fuel injection
pump 16. An engine speed detection sensor 7 is provided in a
flywheel 18. Further, a cooling water temperature detection sensor
14 is provided in the engine main body 1. The engine load detection
sensor 6, the engine speed detection sensor 7 and the cooling water
temperature detection sensor 14 are respectively connected by
wiring to a judging device 13 which is in detail described
below.
As shown in FIG. 1, a first temperature sensor 11 is provided
between the suction air filter 10 of the suction air path 3 and the
joint portion 9. Further, a second temperature sensor 12 is
provided in a downstream side of the joint portion 9 of the suction
air path 3.
Respective detection signals detected by the first temperature
sensor 11, the second temperature sensor 12, the engine load
detection sensor 6, the engine speed detection sensor 7 and the
cooling water temperature detection sensor 14 are respectively
transmitted to the judging device 13 via wiring. The judging device
13 outputs a command to an EGR control device 8 on the basis of the
respective input detection signals, and the EGR control device 8
appropriately regulates an opening degree of the EGR valve 5.
The judging device 13 is provided with a CPU 20 and a memory 19 (a
memory means). An appropriate value of a temperature (hereinafter,
refer to as a downstream temperature) of an appropriate mixed air
(a suction air containing an EGR gas) within the suction air path 3
(an installation position of the second temperature sensor 12) in a
downstream side from the joint portion 9 corresponding to a
combination of the engine load, the engine speed and a suction air
temperature (hereinafter, refer to as an upstream temperature)
between the suction air filter 10 and the joint portion 9 (in an
installation position of the first temperature sensor 11) is
previously determined on the basis of an experiment. This is stored
as a map in the memory 19. The CPU 20 executes various arithmetic
operations and judgments mentioned below. The exhaust gas
recirculation control device for the diesel engine 100 is
structured as mentioned above.
FIG. 2 is a graph comparing one example of an appropriate value (a
standard mixed gas temperature Ts: mentioned below) of a downstream
temperature T.sub.2 changing in correspondence to the change of the
engine load and the engine speed, with an upstream temperature
T.sub.1. The standard mixed gas temperature Ts is uniquely defined
on the basis of the combination of the engine load and the engine
speed mentioned above, as far as the diesel engine 100 is
normal.
In FIG. 2, the suction air temperature after being mixed, which is
uniquely defined on the basis of the engine load and the engine
speed in the standard condition is hereinafter called as the
standard mixed gas temperature Ts. A target value of the downstream
temperature obtained by compensating the standard mixed gas
temperature Ts by the upstream temperature T.sub.1 detected by the
first temperature sensor 11 is called as a compensated mixed gas
temperature Tmr. Further, the suction air temperature within the
suction air path 3 in the upstream side from the joint portion 9 in
FIG. 1 is called as the upstream temperature T.sub.1, and the
suction air temperature within the suction air path 3 in the
downstream side from the joint portion 9 is called as the
downstream temperature T.sub.2.
(Embodiment of the Invention of Claim 1)
In the case that the diesel engine 100 is started, and the engine
load and the engine speed do not rapidly change (for example, at an
idling time after a warm-up is finished), the judging device 13
compares the suction air temperature T.sub.1 before being mixed
with the exhaust gas (the EGR gas) detected by the first
temperature sensor 11, the temperature range on the map stored in
the memory 19 corresponding to the combination of the engine load
and the engine speed respectively detected by the engine load
detection sensor 6 and the engine speed detection sensor 7, and the
actual downstream temperature T.sub.2 detected by the second
temperature sensor 12. At this time, in the target value of the
downstream temperature, it is preferable to compensate the
compensated mixed gas temperature Tmr by the upstream temperature
T.sub.1 (compensate the compensated mixed gas temperature Tmr
higher in accordance that the upstream temperature T.sub.1 becomes
higher and inversely compensate the compensated mixed gas
temperature Tmr lower in accordance that the upstream temperature
T.sub.1 becomes lower), and compare the compensated mixed gas
temperature Tmr after the compensation with the downstream
temperature T.sub.2.
If the downstream temperature T.sub.2 is within the temperature
range on the map, the judging device 13 judges that the EGR gas
amount is appropriate. On the contrary, in the case that the
downstream temperature T.sub.2 is smaller than the temperature
range on the map, the judging device 13 judges that the EGR gas
amount comes short, and in the case that the downstream temperature
T.sub.2 is larger than the temperature range on the map, the
judging device 13 judges that the EGR gas amount is excess. At this
time, it is possible to inform an operator of an abnormality by
lighting an alarm lamp or sounding a buzzer. Further, at this time,
the diesel engine 100 may be stopped in some intended use of the
diesel engine 100.
(Embodiment of the Invention of Claim 2)
In the embodiment in accordance with the invention on the basis of
the first aspect, in the case that the judging device 13 judges
that the EGR gas amount is small (the EGR rate is low), the judging
device 13 outputs a command to the EGR control valve 8 so as to
increase the opening degree of the EGR valve 5 (so as to make the
EGR rate high) in such a manner that the EGR gas amount becomes
appropriate.
On the contrary, in the case that the judging device 13 judges that
the EGR gas amount is large (the EGR rate is high), the judging
device 13 outputs a command to the EGR control valve 8 so as to
reduce the opening degree of the EGR valve 5 (so as to make the EGR
rate low) in such a manner that the EGR gas amount becomes
appropriate. The opening degree of the EGR valve is regulated in
the manner mentioned above, and the EGR gas amount becomes
appropriate.
The EGR rate is uniquely defined by the engine load and the engine
speed, however, the downstream temperature is uniquely determined
by taking into consideration the upstream temperature T.sub.1
detected by the first temperature sensor 11 in addition thereto.
Further, if the upstream temperature T.sub.1 is increased, the
exhaust gas temperature (the EGR gas temperature) is increased, so
that the downstream temperature T.sub.2 detected by the second
temperature sensor 12 is increased.
Accordingly, it is necessary to compensate the downstream
temperature (the standard mixed gas temperature Ts) in the normal
state which is compared with the downstream temperature T.sub.2
detected by the second temperature sensor 12, for example, in
accordance with the following equation (1). It is possible to
secure an appropriate EGR rate on the basis of the equation (1).
Tmr=Ts+(T.sub.1-T.sub.0)/293.times.Tex.times.EGR (1)
where Tmr is compensation mixed gas temperature, Ts is standard
mixed gas temperature, T.sub.1 is upstream temperature, T.sub.0 is
standard suction air temperature (K), Tex is standard exhaust gas
temperature (K), and EGR is EGR rate.
If the upstream temperature T.sub.1 changes as shown in FIG. 2, the
downstream temperature T.sub.2 also changes following thereto.
While the upstream temperature T.sub.1 displaces near the standard
temperature, the downstream temperature T.sub.2 deflects from the
allowable range due to various reasons.
As shown in FIG. 2, the downstream temperature T.sub.2 at a time
t.sub.A is affected by the suction air temperature T.sub.1,and
deviates from the allowable range on the basis of the standard
mixed gas temperature Ts. On the contrary, the downstream
temperature T.sub.2 at the time t.sub.A exists within the
appropriate range on the basis of the compensated mixed gas
temperature Tmr compensated by the suction air temperature T.sub.1
and is not abnormal. Thereafter, when running into a time t.sub.B,
the EGR gas amount is increased (the EGR rate is increased) on the
basis of the clogging of the filter or the clogging of the muffler,
the downstream temperature T.sub.2 at the time t.sub.B deviates
from the appropriate range on the basis of the compensated mixed
gas temperature Tmr, and the judging device 13 determines that the
downstream temperature T.sub.2 at the time t.sub.B is abnormal.
The standard mixed gas temperature Ts is previously determined by
an experiment, however, the standard mixed gas temperature Ts is
uniquely defined on the basis of the engine load and the engine
speed. Further, the standard mixed gas temperature Ts changes
following to the change of the suction air temperature (the
upstream temperature T.sub.1 ). This relation is previously stored
as the equation (1) mentioned above in the memory 19.
If the upstream temperature T.sub.1 is changed, the downstream
temperature T.sub.2 actually measured in the case that the EGR gas
amount is normal undergoes a transition within a region (an
appropriate range) sandwiched by two narrow lines. On the contrary,
if the downstream temperature T.sub.2 deviates from the range
between two narrow lines, it is possible to determine that the EGR
gas amount is abnormal.
FIG. 3 is a graph comparing the change of the downstream
temperature T.sub.2 actually measured by the second temperature
sensor 12, with the compensated mixed gas temperature Tmr
corresponding to the appropriate value of the downstream
temperature on the map. In FIG. 3, an upper limit and a lower limit
of the appropriate range of the downstream temperature are set
around the compensated mixed gas temperature Tmr. If any trouble is
generated and the downstream temperature T.sub.2 deviates from the
appropriate range, the judging device 13 compensates the opening
degree of the EGR valve 5 so as to make the downstream temperature
T.sub.2 be within the appropriate range.
FIG. 4 is a graph showing a relation between the opening degree of
the EGR valve 5 and the engine load. In the case that the
downstream temperature T.sub.2 deviates from the appropriate range,
it is effective to shift the map itself from the standard value as
shown in FIG. 4, for example, in accordance with the equation (1).
Further, it is possible to compensate by changing a slope (a
coefficient) of the graph.
In the case that the opening degree of the EGR valve 5 is not
normal, a map shift corresponding to a fixed amount compensation of
the opening degree is effective. With respect to a change of a
pressure difference caused by the clogging of the suction air
filter 10 and the muffler 15, it is effective to change a slope of
a straight line of the graph.
(Embodiment of the Invention of Claim 3)
Since the temperature sensor has a calorific capacity by itself, a
response delay is generated. The invention in accordance with the
third aspect of the present invention copes with the response delay
of the second temperature sensor 12 at a time of carrying out the
inventions in accordance with the first and second aspects.
In the case that the downstream temperature T.sub.2 detected by the
second temperature sensor 12 temporarily has a large difference
from the compensated mixed gas temperature Tmr because the
downstream temperature can not follow the rapid change of the
engine load and the engine speed, the judging device 13 outputs a
command of compensating the opening map of the EGR valve 5 to the
EGR control device 8 in each case, and there is a risk that the
combustion becomes unstable. In other words, if the judging device
13 faithfully judges on the basis of the detection signal of the
second temperature sensor 12, the signal indicating that the EGR
gas amount is abnormal is input to the state in which the
appropriate EGR gas amount has been actually established, the
opening degree of the EGR valve 5 is changed, and there is further
considered that the combustion is deteriorated so as to discharge
the smoke and the NOx.
In order to avoid the matter mentioned above and stabilize the
combustion, it is preferable to employ a forward moving average
method described below. The forward moving average method is a
method of obtaining a calculated value A5 by substituting, for
example, past four time values (calculated values) A1 to A4 of the
detection value detected by the engine load detection sensor 6 and
the engine speed detection sensor 7, and this time actually
measured value B5 for an equation (2), and employing the calculated
value A5 in place of the actually measured value B5.
A5=(A1+A2+A3+A4+B5)/5 (2)
In the same manner, a value A6 is calculated by the following
equation (3). A6=(A2+A3+A4+A5+B6)/5 (3)
In the calculated values A1 to AX calculated in the manner
mentioned above, a fluctuation band becomes small in comparison
with the actually measured values B1 to BX. In addition, if the
calculated values A1 to AX having the small fluctuation band are
employed as the signal judged by the judging device 13 in place of
the actually measured values B1 to BX, the combustion of the diesel
engine 100 becomes stable. Even if the actually measured values B1
to BX deviate from the appropriate range, the calculated values A1
to AX exist within the appropriate range, and it is possible to
well reduce the discharge of the NOx and the smoke
simultaneously.
FIG. 5 is a graph showing a change of the downstream temperature
T.sub.2 with respect to the load change. Since the second
temperature sensor 12 itself has a calorific capacity, the output
value (the downstream temperature T.sub.2) of the second
temperature sensor 12 follows gradually behind time as shown in
FIG. 5, in the case that the engine load is rapidly changed (the
same matter is applied in the engine speed).
A problem caused by the matter that the actual EGR gas amount and
the temperature detection by the second temperature sensor 12 do
not correspond at real time can be solved by calculating the
compensated mixed gas temperature Tmr on the basis of the engine
speed detection signal and the engine load detection signal in
which the fluctuation band is suppressed by the forward moving
average method mentioned above. In addition, it is possible to
solve the problem caused by the response delay by averaging the
compensated mixed gas temperature Tmr calculated by using the
engine load detection signal and the engine speed detection signal
input to the judging device 13, and suppressing the fluctuation
band.
Further, in some operation aspect of the diesel engine 100, there
is achieved an effect of stabilizing the combustion even if the
operation of the EGR valve 5 is slowly executed. Further, on the
assumption that the output of the second temperature sensor 12
always gets behind the output of the engine load detection signal
and the engine speed detection signal (for example, for one
second), it is possible to make the difference between the actual
temperature and the detected temperature only by delaying at a
predetermined time (for example, one second) as shown by reference
symbol D in FIG. 5.
(Embodiment of the Invention of Claim 4)
If the suction air filter 10 is clogged or the foreign material is
clogged in the muffler 15, a mixing rate between the air and the
EGR gas (an EGR rate) is changed even if the opening degree of the
EGR valve 5 is appropriate. Accordingly, there is a case that
whether or not the suction air filter 10 and the muffler 15 are in
a clean state adversely affects the combustion of the diesel engine
100.
Further, since the deterioration of the suction air filter 10 and
the muffler 15 makes progress slowly, it is not necessary to always
monitor. In the case mentioned above, the judgment by the judging
device 13 is executed at a time when the combustion is
comparatively stable such as an idle operation time or the like. In
particular, in the diesel engine for the motor vehicle, the
operation state tends to be rapidly changed (changed in load).
Accordingly, the judgment is not executed at a time of a normal
operation, but is executed only at a time when the combustion is
stable. In accordance with the structure mentioned above, the
downstream temperature T.sub.2 (the EGR gas amount) does not
deviate largely from the appropriate range even at a time of the
normal operation, and it is possible to reduce the discharge of the
NOx and the smoke even in the diesel engine 100 for an intended use
in which the load change and the rotational change are large.
FIG. 6 is a graph comparing the change of the engine load with the
downstream temperature. In FIG. 6, the load change becomes smaller
after a time t. Accordingly, the detection is executed by each of
the sensors from the time t to the time t1, and the judgment by the
judging device 13 is executed on the basis thereof.
(Embodiment of the Invention of Claim 5)
In the cooling condition (when the engine temperature during the
warm-up or the like is low), it is hard that each of the sensors
executes a normal detection. If the opening degree, for example, of
the EGR valve 5 is changed at that time, it is unavoidable to
deviate from the appropriate value. Accordingly, the judgment by
the judging device 13 is executed at a timing when the combustion
is stabilized except the cooling condition as mentioned below.
The judging device 13 is provided with a function of detecting the
end of the warm-up, and recognizes that the diesel engine 100
finishes the warm-up on the basis of the signal input from the
cooling water temperature sensor 14. If the judging device 13
recognizes that the warm-up is finished, the judging device 13
receives the detection signal from each of the sensors before
starting the normal operation so as to judge whether or not the EGR
gas amount is appropriate.
In the embodiment mentioned above, there is shown the embodiment
that the judgment is executed at a time of the idle operation just
after the warm-up is finished, however, the structure may be made
such that the judgment is executed before stopping the diesel
engine 100 after the operation of the diesel engine 100 is
finished.
(Embodiment of the Invention of Claim 6)
FIG. 7 is a graph showing a relation between the axial mean
effective pressure and the engine speed per the different EGR rate.
Further, FIG. 8 is a graph showing a relation between an exhaust
gas regulation allowable range limited by the allowable smoke
amount and the allowable NOx amount contained in the exhaust gas,
and the EGR rate of the diesel engine 100.
In the case that the compensated mixed gas temperature Tmr on the
map stored in the memory 19 corresponding to the engine load, the
engine speed and the upstream temperature T.sub.1 detected by the
engine load detection sensor 6, the engine speed detection sensor 7
and the first temperature sensor 11 deviate from the actual
downstream temperature T.sub.2 detected by the second temperature
sensor 12 at a predetermined temperature (for example, 30.degree.
C.) or more, an abnormality is aroused in the diesel engine 100 by
lighting an alarm lamp or sounding an alarm buzzer.
Since the high-temperature EGR gas amount is increased in
accordance with the increase of the EGR rate, the suction air
temperature becomes higher. Further, as shown in FIG. 8, the
discharge amount of the smoke is increased in accordance with the
increase of the EGR rate.
In the case that the EGR gas amount is increased on the basis of an
erroneous operation (an excessive opening) of the EGR valve 5, the
EGR rate undergoes a transition within the exhaust gas regulation
allowable range region (a hatched region in FIG. 8) along the EGR
curve A. On the contrary, there is a case that the EGR rate is
increased because the pressure balance between the air pressure and
the EGR gas pressure is unbalanced due to the clogging of the
suction air filter 10 and the muffler 15. At this time, the suction
air amount of the diesel engine 100 itself is reduced, so that an
oxygenless state is generated. At this time, the EGR rate undergoes
a transition along the EGR curve B, and deviates from the exhaust
gas allowable range region earlier than the EGR curve A, and the
smoke is rapidly deteriorated.
Accordingly, it is necessary to make a judging level (margin)
severe in the side in which the EGR rate is increased, that is, the
side in which the downstream temperature T.sub.2 is higher than the
standard mixed gas temperature Tmr. A degree of severity is changed
in accordance with the engine load, however, it is preferable to
set to about 50% of the EGR rate reduction side in the operation
region having the high engine load (about 50% to 100% of a rated
engine load), and set to about 80% of the EGR rate reduction side
in the operation region having the low engine load (about 50% or
less of the rated engine load).
For example, in the operation region having the high engine load,
in the case that the EGR abnormality is judged if the downstream
temperature T.sub.2 actually measured by the second temperature
sensor 12 is lower by 30.degree. C. or more than the compensated
mixed gas temperature Tmr on the map in the EGR rate reduction side
(the side where the EGR gas amount is short), it is set such that
if the downstream temperature T.sub.2 actually measured by the
second temperature sensor 12 becomes higher by 15.degree. C. or
more than the compensated mixed gas temperature Tmr on the map in
the EGR rate increase side (the EGR gas amount excess side), the
judging device 13 judges the EGR abnormality.
On the contrary, in the operation region having the low engine
load, in the case that the EGR abnormality is judged if the
downstream temperature T.sub.2 actually measured by the second
temperature sensor 12 is lower by 30.degree. C. or more than the
compensated mixed gas temperature Tmr on the map in the EGR rate
reduction side, it is set such that if the downstream temperature
T.sub.2 actually measured by the second temperature sensor 12
becomes higher by 24.degree. C. or more than the compensated mixed
gas temperature Tmr on the map in the EGR rate increase side, the
judging device 13 judges the EGR abnormality.
In the case that the downstream temperature T.sub.2 deviates from
the standard mixed gas temperature Ts at the predetermined
temperature or more as mentioned above, the judging device 13
judges that an abnormal state is generated, and takes a measure,
for example, of generating an alarm, stopping the diesel engine
100. As a result, it is possible to suppress the discharge of both
the smoke and the NOx.
(Embodiment of the Invention of Claim 7)
FIG. 9 is a graph further compensating the compensated mixed gas
temperature Tmr while taking the cooling water temperature into
consideration. Taking the cooling water temperature into
consideration in the equation (1) mentioned above, an equation (4)
(a compensating means) is obtained.
Tmr=Ts+(T.sub.1-T.sub.0).times.{Tex-al.times.(Tw.sub.0-Tw)}.times.EGR/293
(4)
where T.sub.0 is standard suction air temperature (K), Tex is
standard exhaust gas temperature (K), Tw.sub.0 is standard cooling
water temperature, Tw is current cooling water temperature, and al
is influence coefficient of cooling water temperature (for example,
0.3 to 0.5 depending on the engine).
In the case that the diesel engine 100 is for the working machine,
the engine load and the engine speed are violently changed, and a
stable region as shown in FIG. 6 is limited to the warm-up just
after starting the engine in many cases.
Since the temperature of each of the parts is low during the
warm-up, and the heat dissipation amount of the EGR gas is
increased, the EGR gas temperature becomes low. Taking the
influence into consideration in the equation (4), it is possible to
accurately judge the EGR gas amount even during the warm-up.
Assuming that the compensated mixed gas temperature Tmr on the map
and the actually measure downstream temperature T.sub.2 necessarily
deviate, in the cooling condition, the compensated mixed gas
temperature Tmr is calculated by employing the equation (4) without
employing the equation (1).
The temperature of the exhaust gas is uniquely defined on the basis
of the engine load and the engine speed. However, if the
temperature of the path in the middle of the exhaust gas (the EGR
gas) flow is low, the heat is absorbed by the path member, and the
temperature of the EGR gas is lowered. In the case of setting the
opening degree of the EGR valve 5 on the basis of the lowered EGR
gas temperature, it is impossible to execute an accurate
judgment.
Therefore, in accordance with the seventh aspect of the present
invention, whether or not the warm-up is executed is judged by
monitoring the way of increasing the cooling water temperature. If
the temperature of the path member absorbing the heat of the
exhaust gas (the EGR gas) is increased, the cooling water
temperature is also increased. For example, it is possible to
approximately estimate whether the EGR gas which is originally
300.degree. C. is lowered to 250.degree. C. or lowered to
200.degree. C. Reflecting it on the equation (4) and arithmetically
operating by the judging device 13, it is possible to appropriately
compensate the compensated mixed gas temperature Tmr.
INDUSTRIAL APPLICABILITY
The exhaust gas recirculation control device in accordance with the
present invention can be applied to various diesel engines.
* * * * *